Wireless networks have experienced increased development in the past decade. One of the most rapidly developing areas is mobile ad hoc networks (MANETs). Physically, a MANET includes a number of potentially geographically distributed, potentially mobile nodes sharing one or more common radio channels. Compared with other types of networks, such as, cellular networks or satellite networks, MANETs have two distinctive features. First, MANETs lack any fixed infrastructure. Second, each node can act as a router to forward an upstream node's traffic to an ultimate destination, potentially many hops distant. The network is formed of mobile (and potentially stationary) nodes, and is created on the fly as the nodes communicate with each other. The network does not depend on any particular node and dynamically adjusts as some nodes join or others leave the network.
MANETs typically use dynamic routing capabilities. A routing algorithm ensures that data takes an appropriate, and hopefully the fastest, route to a destination node. Some MANETs could include multiple fixed base stations with “cut through” high bandwidth terrestrial links operating as gateways to fixed base stations or other services, including the Internet. It is possible to extend the mesh network with only a minimal base station infrastructure. There are also many different types of routing protocols that can be used in a mesh network, for example, an Ad hoc On-Demand Distance Vector (AODV), Dynamic Source Routing (DSR), Optimized Link State Routing protocol (OLSR) and Temporally-Ordered Routing Algorithm (TORA).
One approach to communication in a MANET may comprise using a Time Division Multiple Access (TDMA) protocol. Depending on the configuration of a TDMA MANET, end-to-end latency (ETEL) can be problematically large. ETEL is the time it takes to deliver a piece of data, typically a data packet, from a source node to a destination node. Thus, ETEL can be referred to as the time duration from when the packet is presented to the data communications layer of the stack at the source node to when the packet is passed up from the data communications layer of the stack at the destination node. MANETs transmit a packet among different intermediate nodes using multiple hops as it traverses the network from a source node to a destination node. In a TDMA network, the channel time slot can be allocated before the node data is transmitted. The channel transmit time is typically allocated in a recurring slot. The channel time typically is segmented into blocks as an epoch and blocks may be divided into slots used by nodes to transmit data.
Depending on the application, a reduced ETEL value may be helpful in achieving good Quality of Service (QoS). For example, interactive two-way speech has demanding ETEL requirements, i.e. this application requires low latency because humans are extremely sensitive to transmission delays. Typical latency needs to less than 150 ms to minimize human-perceptible objections and problems, for example, talking “over” each other in long-distance satellite conversations due to satellite delay. An approach to improving ETEL in TDMA based MANETs is disclosed in U.S. Pat. No. 7,894,416 to Rudnick et al., assigned to the present application's assignee, the contents of which are incorporated by reference in their entirety. In this MANET, the transmission ETEL may be reduced by scheduling time slot allocations in the epoch based upon the link placement in the path.